Exemplary embodiments of the invention relate to a rotor hub fairing system, and more particularly, to a rotor hub fairing system that reduces overall drag for a high speed rotary wing aircraft having a counter-rotating, coaxial rotor system.
Typically, aerodynamic drag associated with a rotor system of a rotary wing aircraft is a significant portion of the overall aircraft drag, commonly 25% to 30% for conventional single-rotor helicopters. The rotor system drag increases for a rotary wing aircraft having a counter-rotating coaxial system primarily due to the additional rotor hub and the interconnecting main rotor shaft assembly between the upper and lower rotor systems. For high speed rotary-wing aircrafts, the increased drag resulting from counter-rotating coaxial rotor system may cause a relatively significant power penalty.
The aerodynamic drag of the dual counter-rotating, coaxial rotor system is generated by three main components—the upper hub, the lower hub, and the interconnecting main rotor shaft assembly. The drag contributions may be approximately 40% for each of the rotor hubs, and 20% for the interconnecting shaft assembly.
Fairings have been used in conventional rotary wing aircrafts to reduce the drag. The implementation of a fairing in an application having airfoils with a large thickness to chord ratio is more complex because of the negative restoring moment of the thick airfoils. By incorporating a more complex mechanism and controller, the benefit of the fairings is ultimately reduced.